1. Field of the Invention
The present invention relates to a water jet cutting technology, and more particularly, to a technology for abrasive water jet cutting by means of a water jet mixed with abrasive.
2. Description of the Related Art
A jet (hereinafter referred to as the “water jet”) is obtained by pressurizing water to a high pressure and forcing it through a nozzle. Then the water jet is mixed with abrasive inside the nozzle, thus producing a water jet with abrasive (abrasive water jet). The abrasive water jet is used to cut a variety of materials. Cutting by means of the abrasive water jet has characteristics that the width of the cut is small and the cutting surface is not affected by heat.
Cutting by means of the abrasive water jet (hereinafter, simply referred to as “water jet cutting”) might cause inclination of the cutting surface depending on the type of material being cut (material of a workpiece) and cutting conditions.
Furthermore, when the cutting speed (relative movement speed of the nozzle to the workpiece) exceeds a predetermined speed determined by the type of material being cut and material thickness, a delay in cutting is caused. When the apex (hereinafter referred to as the “corner portion”) of a curve or a polygonal line in the cutting shape is drawn under the condition of a remarkable delay in cutting, an uncut portion occurs on the surface of the workpiece far away from the nozzle.
Therefore, in order to eliminate the delay in cutting, a method is proposed in which the inclination angle of the cutting surface on a necessary side (product side) after cutting is controlled by appropriately inclining the axis of the nozzle during cutting rather than directing it perpendicular to a cutting direction (relative movement direction of the nozzle to the workpiece) (see Japanese Examined Patent Application Publication No. Hei 6-45120 and Japanese Patent No. 5266169).
The Japanese Examined Patent Application Publication No. Hei 6-45120 does not disclose a method for estimating an advance angle α and a taper correction angle β as a basis of the attitude control, and therefore the technology disclosed therein cannot be used directly as a system for automatically controlling cutting process.
Furthermore, with the technology disclosed in Japanese Patent No. 5266169, there is a need for an operator to create a new cutting program on the proposed system for changing cutting speed and adjusting cutting time. However, it takes time and effort to create a new cutting program from the cutting shape at each change in cutting speed for the purpose of obtaining the same cutting shape. Further, since such system causes many different cutting programs depending on cutting shapes and cutting parameters, it is inconvenient to arrange and store the cutting programs.